This invention relates to the field of surgical devices used primarily for the repair or replacement of human tissue including, but not limited to, the nucleus pulposus of the spine. This invention further relates to the method of implanting such devices.
The spinal column is a flexible chain of closely linked vertebral bodies. In a normal human spine there are seven cervical, twelve thoracic and five lumbar vertebral bodies. Below the lumbar vertebrae are the sacrum and coccyx. Each individual vertebra has an outer shell of hard, dense bone. Inside the vertebra is a honeycomb of cancellous bone containing red bone marrow. All of the red blood cells, and many of the white blood cells, are generated inside such cancellous bone, where the blood cells mature before being released into the blood circulation.
The spinal disc serves as a cushion between the vertebral bodies so as to permit controlled motion. A healthy disc consists of three components: a gelatinous inner core called the nucleus pulposus; a series of overlapping and laminated plies of tough fibrous rings called the annulus fibrous; and two (i.e., superior and inferior) thin cartilage layers, connecting the disc to the thin cortical bone of the adjacent vertebral bodies, called the end plates.
The spinal disc may be displaced or damaged due to trauma or disease, such as a herniation or degenerative disc disease.
A herniated disc may bulge out and compress itself onto a nerve, resulting in lower leg pain, loss of muscle control or paralysis. To treat a herniated disc, the offending nucleus portion is generally removed surgically.
Disc degeneration gradually reduces disc height, forcing the annulus to buckle, tear or separate radially or circumferentially, and causing persistent and disabling back pain. Degenerative disc disease is generally treated by surgically removing the nucleus and fusing the adjacent vertebral bodies so as to stabilize the joint.
In either case, whether removing some or all of the nucleus, these procedures ultimately place greater stress on adjacent discs to compensate for the lack of motion, which may in turn cause premature degeneration of those adjacent discs.
It has been recognized that it may be possible to replace the excised nucleus with a prosthetic implant, whereby to restore the spinal disc to its original configuration and function. Unfortunately, such implants, sometimes referred to as a prosthetic nucleus, tend to suffer from one or more deficiencies.
One deficiency of current prosthetic nuclei is that the annulus is further weakened by either large or multiple cut-outs which are required in order to insert the prosthetic nucleus into the interior of the spinal disc. Additionally, any flaps or cut-outs of the annulus are not easily repaired; thus, there may be a concern that the prosthetic nucleus may eventually work its way back out of the disc space. A further deficiency of current, less-invasive prosthetic nuclei (see, for example, U.S. Pat. No. 5,674,295, issued Oct. 7, 1997 to Ray et al.) is that multiple, laterally-spaced implants typically have to be used, which suggests that the side-by-side positioning of the several implants has to be carefully considered so as to ensure proper load carrying.
Modern trends in surgery include the restoration of bodily function and form (i.e., the repair) of anatomical structures through the use of minimally invasive surgical techniques. The ability to surgically repair damaged tissues or joints, creating as few and as small incisions as possible, generally produces less trauma, less pain and better clinical outcomes for the patient.
It is, therefore, one object of the present invention to provide an apparatus and minimally invasive method for delivering material into human tissue.
Another object of the present invention is to provide an apparatus and method for delivering an implant into the inner portion of a damaged intervertebral disc for restoration of the disc. The implant is inserted through a small opening in the annulus of the disc so as to replace the natural nucleus pulposus of the disc.
These and other objects are addressed by the present invention.
More particularly, one feature of the present invention is the provision of an apparatus and method for delivering a small, flexible implant which expands in biologic tissue. The apparatus and method for delivering the small, flexible implant into biologic tissue comprises the following steps:
(a) accessing and preparing the intended insertion space;
(b) inserting into the space, through a cannula or otherwise, the small flexible implant that is expandable through memory, hydration or otherwise; and
(c) after insertion into the space, the small flexible implant expands so as to form a second shape which is larger than the shape of the implant during insertion.
Steps (a) through (c) may be performed through open or minimally invasive surgical techniques.
Another feature of the present invention is the provision of a prosthetic nucleus for implantation in a chamber of an intervertebral disc after removal of at least a portion of a damaged or degenerated nucleus from the chamber. The prosthetic nucleus comprises a wafer of biologically compatible, thin, flexible, and expandable material in a selected first configuration, the wafer being adapted to be re-shaped mechanically into a compact second configuration of cross-section sufficiently small to permit travel of the wafer through a cannula and into the disc chamber, the wafer being adapted to substantially regain the first configuration thereof by memory upon entry into the disc chamber, and the wafer being adapted to react to an expansion-inducing agent in the disc chamber to expand to an enlarged and selected third configuration.
In accordance with a further feature of the present invention, there is provided a prosthetic nucleus for implantation in a chamber of an intervertebral disc after removal of at least a portion of a damaged or degenerated nucleus from the chamber. The prosthetic nucleus comprises a wafer of biologically compatible and expandable material in a selected first configuration. The wafer is adapted to be collapsed into a compact second configuration of cross-section sufficiently small to permit travel of the wafer through a cannula and into the disc chamber, and the wafer is adapted to react to an expansion-inducing agent in the disc chamber to expand to an enlarged and selected third configuration.
In accordance with a further feature of the present invention, there is provided a prosthetic nucleus for implantation in a chamber of an intervertebral disc after removal of at least a portion of a damaged or degenerated nucleus from the chamber. The prosthetic nucleus comprises a wafer of biologically compatible, thin, flexible, and expandable material in a selected first configuration. The wafer is adapted to be re-shaped mechanically into a compact second configuration of cross-section sufficiently small to permit travel of the wafer through a cannula and into the disc chamber. The wafer is adapted to substantially regain the first configuration thereof by memory upon entry into the disc chamber, and the wafer is adapted to react to an expansion-inducing agent introduced into the wafer to expand to an enlarged and selected third configuration.
In accordance with a still further feature of the present invention, there is provided a prosthetic nucleus for implantation in a chamber of an intervertebral disc after removal of at least a portion of a damaged or degenerated nucleus from the chamber. The prosthetic nucleus comprises a plurality of wafers of biologically compatible and expandable material, each in a selected first configuration. The wafers are adapted to be re-shaped mechanically into a compact second configuration of cross-section sufficiently small to permit travel of the wafers through a cannula and into the disc chamber. The wafers are adapted to substantially regain the first configuration thereof by memory upon entry into the disc chamber, and are adapted to react to an expansion-inducing agent to expand to an enlarged and selected third configuration.